This invention relates to a sound translation system and more particualrly to a system that is specifically configured for use in the translation of a single channel (monaural or mono) audio signal to a multi-channel (stereophonic or stereo; quadraphonic; surround sound) audio signal for presentation in a variety of forms.
Specifically, the invention is directed to uniquely employing non-reverberative, linear, high-fidelity, variable, digital time delay means for the production of pleasing and realistic multi-channel audio output information from monaural input which may originate from live performance or such as mechanical, magnetic, optical, digital or broadcast audio reproduction means. Pre-existing stereo channels may be individually utilized or summed whereby monaural input is provided to the invention for quadraphonic or surround sound applications.
This invention is NOT a reverberative device and presupposes sufficient reverberation content to exist in monaural input audio source material. It is a feature of the invention to achieve a stereo-like output from mono input without significantly adding to reverberation content in output signal.
Current research indicates that the human brain manifests an active role in the processing and interpretation of of binaural audio information whereby factors such as phase, arrival time and amplitude are organized as to provide the listener with perception of sonic dimensions. Since it is binaural stimulus reception, and not production of sound that is responsible for perception of depth and direction, stereophonic sound may be said to only exists in a listener's brain.
When considering the natural auditory phenomenon of echo, a simple geometric rule prevails: The shortest distance between two points is a straight line. Accordingly, the distance that a given sound must travel to a listener, from a given source, is always shorter from a direct route than from a reflective route. Traveling the greater distance, the reflective signal is always of greater delay time and less amplitude than is the direct signal. In nature, therefore, it may be said that an INVERSE relationship always exists between delay time and amplitude.
As the principle of the invention, a DIRECT relationship is established between delay time and amplitude. That is to say, the time delayed signal is ALWAYS of greater amplitude than the undelayed signal. By this unique means of the invention, the listener is provided an amplitude/delay binaural audio stimulus which is in conflict with that found in nature.
In conjunction with the above principle, many embodiments of the invention uniquely employ phase inverted paired signals (PIPS), which may not be found in nature, whereby two signals, of equal frequency content and amplitude but 180 degrees out of phase with one another, are uniquely presented from separate output channels, as to produce the means for controlling width and/or depth perceptual dimensions and timbre-related separation effects while also providing the means for achieving excellent monaural compatability characteristics.
Frequemcy filtering is employed in several embodiments of the invention in the context of the above cited time, amplitude and phase realatinships.
It is not known if the means of the invention produces true stereo from mono input. It is the purpose of the invention to utilize relationships not found in nature whereby the listener's brain is caused to perceive a pleasant and realistic three dimensional sonic effect not unlike true stereophonic sound.